Virtual cooperating manipulators as a virtual reality haptic interface

Abstract

One central element in the focus on research into human-machine interfaces is the capability to interact physically with the computer model. The sense of touch and feel is vital for realistic manipulation and control of virtual objects. The research described here is the development and implementation of a new dynamic control strategy using a standard six-degree-of-freedom robot manipulator as a force interface to virtual reality systems. The haptic element of VR interfacing is currently the subject of abundant research, some addressing the stability and control of interactive systems but with much of the focus on the development of new hardware systems to support stable interaction between humans and VR graphics displays. However, general six-degree-of-freedom manipulators are well understood today and are known to have the capability for generating the general force and motion constraints necessary for the design interaction described in the story. This approach to haptic feedback capability is based on the concept of describing a virtual manipulator model that mimics the motion constraints imposed by a virtual surface. This virtual manipulator is conceptually linked to an actual manipulator to form a closed kinematic chain system. The closed chain system equations are used to define a set of constraints that control the actual robot manipulator so as to allow motion only in the free directions of the virtual manipulator. These free directions are also the free motion directions allowed by the virtual surfaces one tremendous advantage of the approach is that the control algorithm is formulated using local error feedback schemes at the robot level providing effective, stable, and simple control of the robotic hardware. Using the proposed control scheme will allow any six-degree-of-freedom manipulator to be used as a haptic interface device.